A method and device of the aforementioned type are known from International Patent Application WO2003030173 (PHNL010708), which is hereby enclosed by reference.
WO 2003/030173 discloses that in an open DVD+R Video Session, a Reserved Fragment of the open session is treated as a virtual rewritable area of 31 Megabyte (MB) size. As is known in the art, the layout of an open DVD Video Session has a data zone with two fragments, which are a Reserved Fragment followed by an Incomplete Fragment. The Reserved Fragment is kept completely unwritten until the Video Session is closed. Data intended for this area of 31 MB is temporarily written into the Incomplete Fragment. The Incomplete Fragment contains all files and file system data that is required to be present in the data zone of a closed DVD Video Session.
The mentioned method and apparatus provide a virtual management area, which is mapped to a real physical location in the Reserved Area by a mapping table. Only when finalizing a disc, that is, when providing the disc with a Lead-In and a Lead-Out area to make the disc playback-compatible, the management data structures are copied to the correct location in the reserved area.
For writing the Reserved Fragment during finalization, the recording device refers to a table stored at the very end of the recorded area in the Incomplete Fragment, the Reserved Space Allocation Table (RSAT). The RSAT provides exact information on the location of temporarily stored data that needs to be copied to the Reserved Fragment. DVD+RW video recording devices write the RSAT in the last written ECC blocks on a DVD+R disc after one or more recordings have been made, or after a playlist or menu editing has been done. This video format is defined in the DVD+R/RW Video format Specifications, which are already introduced in the market.
In the United States, as of 1 Jul. 2005, digital video recorders have to encrypted recorded television (TV) broadcasts that carry a Broadcast Flag. The Broadcast Flag is a digital code that can be embedded into a digital broadcasting stream according to the regulations of the U.S. Advanced Television Systems Committee (ATSC). A similar regulation in Japan already requires the encrypted recording of digital TV broadcast signals.
The aim of introducing this method of information content encryption is to prevent unlicensed mass distribution over the Internet. An example of a content protection system, which is in accordance with the Broadcast Flag rules is the known Video Content Protection System (VCPS) for disc-like recording media such as recordable Digital Versatile Discs (DVD+R) and rewritable Digital Versatile Discs (DVD+RW). VCPS also enables direct digital recording of “copy-once” content from satellite and cable sources.
According to the VCPS system, a disc containing encrypted content is provided with a unique identification code, hereinafter Unique ID, which is a 40-bit random number that is deposited on the disc by a recording device recording encrypted content according to the VCPS. An example of a recording device is an optical drive of a personal computer, which is adapted to record DVDs or a consumer electronics DVD recorder.
A disc containing content encrypted according to the VCPS also stores a Disc Key Block (DKB), which is a list of encrypted keys. VCPS-compliant devices for reproducing the encrypted content, such as a DVD video player, are provided with an individual Hardware Device Key (HDK). Software players and recorders are provided with a Software Device Key (SDK). Encrypting and decrypting information content involves calculating a special key, which is a function of the HDK/SDK, the Unique ID of the individual disc and the Disc Key Block stored on the disc. More information on VCPS can be found on the Internet at the URL http://www.licensing.philips.com/vcps.
When finalizing the disc, a DVD+RW video recorder fills the Reserved Fragment with file system data and DVD menu files. Examples of such menu files are IFO files including information on, for instance, chapters, subtitle tracks and audio tracks, or VOB files containing actual video objects such as movie files with video/audio data.
In finalizing a disc also a Lead-in-Zone located at the inner side of the disc is recorded. The structure of the Lead-In-Zone as a part of the video format is well known in the art, and is for instance found in the standard ECMA-349, second edition, June 2004, pages 55 to 58. The Lead-In-Zone contains a so-called Buffer Zone 2.
However, in DVD+R and DVD+RW discs containing a session recorded according to the VCPS, the Unique ID and the Disc Key Block are stored in Buffer Zone 2. According to VCPS, as soon as a first encrypted A/V recording is added to the disc, Buffer Zone 2 is written to contain the Unique ID and the Disc Key Block. This use of Buffer Zone 2 is not reserved for the purposes of VCPS by other disc standards. Thus, if such a disc is finalized by a recording device not familiar with VCPS, that device will be unaware of the fact that Buffer Zone 2 contains essential VCPS data, namely, the Unique ID and the Disc Key Block necessary to decrypt encrypted content on the disc. In writing the Lead-In-Zone according to a standard recording method not compliant with VCPS, Buffer Zone 2 will therefore be overwritten. The Unique ID and the Disc Key Block will be destroyed. As a result, the encrypted video content can not be decrypted anymore.
In other words, legacy (non-VCPS) video recorders are not aware of any content protection that may have been applied. They might finalize the disc, which includes writing the complete Lead-In area, thereby destroying the Unique ID and the Disc Key Block, rendering the encrypted content non-decryptable for legacy devices as well as VCPS-compliant devices.